In order to obtain chemotherapeutic agents with selective affinity for the prostate, steroidal cytotoxic agents specifically designed to bind to prostatic binding protein (prostatein) will be prepared. The steroidal components will, respectively, have (i) weak estrogenic activity, (ii) 5 Alpha-reductase-inhibiting activity and (iii) be hormonally inert. It is expected that they will bind to prostatic protein and be enzymatically hydrolyzed therein, with release of the cytotoxic and steroidal components. Their successful development will provide, for the first time, a group of cytotoxic steroids concentrating in the prostate and possessing a spectrum of therapeutic activities rendering them potentially suitable for the treatment of both hormone-responsive and hormone-unresponsive tumors. The steroids per se and the derived cytotoxic steroids will be screened for affinity to prostatic protein. Effects upon DNA synthesis and, where appropriate, 5 Alpha-reductase-inhibiting activity and endocrine activity, will be determined. Samples will be sent to Dr. Avery Sandberg for study in human prostatic tissue explants in organ culture. L.D.50 determinations will be made and effects upon growth and morphology of the prostate in the intact rat will be established, thus opening the way to subsequent antitumor studies in the rat.